1. Field of the Invention
The present invention pertains to packers of the type used to seal the interior of a well, either cased or uncased, with respect to the exterior of a string of drill stem, tubing or the like. In particular, the invention pertains to packers of the inflatable type in which a packer element, carried by a suitable tool, is placed in the well at the proper depth and then inflated with fluid pressure to seal against the inner surface of the well bore, casing or the like. Such packers find numerous uses in the drilling, production, and/or servicing of wells for the recovery of petroleum, natural gas, water, etc. For example, in connection with oil wells, such inflatable packers may be used to seal off an oil/water interface, to isolate a lost circulation zone of the well, to isolate various zones of the well for testing purposes, etc.
2. Description of the Prior Art
In inflatable packers, a valve or other mechanism is needed to control inflation and setting of the packer element after it has been properly positioned in the well. That mechanism or another one must then operate to deflate the packer element, unless it is to remain permanently set.
One such type of valve commonly employed makes use of shear pins to hold a valve member in a normally open or closed position. Fluid pressure build-up acting on the valve element causes the pins to shear so that the valve element will move to the desired position. Examples of such valves may be found in U.S. Pat. Nos. 3,053,322 to Kline, 3,503,334 to Cockrum et al., and 3,160,211 to Malone. The use of shear pins has several disadvantages. For one, the pins may be accidentally broken allowing premature operation of the valve. Secondly, once the shear pins have been broken, the valve element cannot be easily reset down hole. Thus, there is necessarily a limit to the number of times the packer can be deflated and reset.
In other packers, such as those shown in U.S. Pat. Nos. 3,085,628 to Malone and 3,552,486 to Burns, valves are opened and/or closed by rotation of either the drill string or of a separate tool from the top of the well. Such devices are expensive and complicated to use. Furthermore, they are subject to jamming and other malfunctions.
Still other inflatable packers, such as that in U.S. Pat. No. 2,994,378 to Reistle, Jr., are operated by non-rotary tools from the top of the well. Again, the procedure is expensive and bothersome.